1. Field of the Invention
This invention relates to a projection aligner (projection exposure apparatus) for performing and exposing so that a pattern drawn on a reticle is projected onto a wafer by light emitted from the light source.
2. Description of the Related Art
A projection aligner is used for manufacturing semiconductor devices. The projection aligner has a light source, a reticle stage with a reticle, a wafer stage with a wafer and a reduction lens(scale-down projection lens). During a projection exposure operation, a pattern on the reticle is projected onto the wafer via the reduction lens by light emitted from the light source.
Recently, the projection aligner is required to have a high-pattern position precision for coping with the latest devices. For increasing the pattern position precision, rising temperatures in the projection aligner by the light emitted from the light source, is not to be disregarded. Pattern position precision is affected by the heat expansion of the reticle or by the changing the distribution of distortion of the reduction lens.